Precision spectroscopy with COMPASS and the observation of a new iso-vector resonance

Abstract

We report on the results of a novel partial-wave analysis based on $50\cdot 10^6$ events from the reaction $π^- + p \to π^-π-^π^+ + p_\text{recoil}$ at 190 $\text{GeV/c}$ incoming beam momentum using the COMPASS spectrometer. A separated analysis in bins of $m_{3\pi }$ and four-momentum transfer $t^{\prime }$ reveals the interference of resonant and non-resonant particle production and allows their spectral separation. Besides well known resonances we observe a new iso-vector meson $a_1(1420)$ at a mass of 1420 $\text{MEV\c}^2$ in the $f_0(980)\pi$ final state only, the origin of which is unclear. We have also examined the structure of the $0^{++}$ $\pi \pi$-isobar in the $J^{PC}=0^{-+},1^{++},2^{-+}$ three pion waves. This clearly reveals the various $0^{++}$ $\pi \pi$-isobar components and its correlation to the decay of light mesons.

8 pages, 7 figures

References in corpus (2)

• Glueballs, Hybrids, Multiquarks. Experimental facts versus QCD inspired concepts
• The COMPASS Experiment at CERN

Cited by in corpus (6)

• Light-Front Holographic QCD and Emerging Confinement
• On the nature of $a_1(1420)$
• Observation of a new narrow axial-vector meson $a_1(1420)$
• Axial resonances a1(1260), b1(1235) and their decays from the lattice
• $a_1(1420)$ resonance as a tetraquark state and its isospin partner
• Light axial-vector tetraquark state candidate: $a_1(1420)$